Inductance device



Dec- 22, 1925. v 1,566,792 F. E. FIELD v INDUCTANCE DEVI CE Filed A rii17, 1922 Patented Dec. 22, 1925.

p v 1,566,792 1 UNITED STATES P'ATENT'. OFFICE.

FRANK E. FIELD,- OF SOMERVILLE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

mnuo'rancn DEVICE.

Application filed April 17, 1922. Serial No. 553,619.

To all whom it may concern:

Be it known that I, FRANK E. FIELD, a citizen of the United States,residin at Somerville, in the county of Somerset, tate of New Jersey,have invented certain new and useful Improvements in Inductance Devices,of which the following is a full, clear, concise, and exact description.

This invention relates to inductance devices and particularly toauto-transformers or repeating coils adapted for use in phantomedtelephone circuits.

An object of this invention is to provide v a method and means foraccurately adjusting the reactances of two inductive windings in orderthat a desired relation may exist therebetween.

Another object is to provide a method and means for locating anintermediate tap for a transformer winding at such a position that thetap will be located in the exact inductive center of the windin Thisinvention will be hereinafter described as embodied in anauto-transformer such as is used in reducing reflection losses inphantom telephone circuits. I

In such a transformer an intermediate tap is usually provided to whichphantom circuit connections are made. If this phantom tap is not locatedat the exact impedance center of the transformer winding, cross talkbetween the side circuit currents and the phantom circuit currents isliable to occur-a result which is highly objectionable. This inventionprovides a simple and reliable method and means for insuring that thetwo halves of the transformer winding are balanced electromagnetically.

In accordance with this-invention the two halves of the windin tobebalanced against each other are woun ondiflerent parts of asubstantially closed magnetic circuit core.

' An adjustable core piece having a few winding turns thereon connectedin circuit with one of the halves of the main winding 'is provided whichcan be moved to such a position that the flux produced by the auxiliaryWinding roduces the same change in flux in both he ves ofthe mainwinding or a greater change in one half than the other. By varying theposition ofthis. auxiliary core piece the desired equalit between theinductance values of the two alves may be readily realired' to anydesired degree of accuracy.

in a* phantomed telephone circuit.

The auto-transformer illustrated in Fi 1 comprises a substantiallyclosed magnetic circuit core 5, one portion of which is surrounded by awinding 6 and another portion of which is surrounded by awinding 7.

A twisted pair winding 8. is also disclosed surrounding the entire corestructure. b The manner in which the terminals 9, 10, 11, 12, and 13 areemployed in connecting the autotransformer in a phantomed telephone'circuit, is shown in Fig. 3, terminals 9, 10 leading to one section ofthe telephone line, term'inals 11, 13 leadingto another section of 4 thetelephone line, and terminal .12 leading to phantom circuit connectionswhereby phantom currents are impressed upon the telephone line sectionconnected to terminals 9 and 10. As shown in Fig. 3, winding,

6 and half of the twisted pair 8 are located on, one side of phantom tap12 while the other half of the'twisted pair 8 andthe winding 7 arelocated on the opposite side of the phantom tap.

In order that cross-talk between the phantom circuit currents and theside circuit currents may berevented it is highly desirable that the pantom circuit tap 12be lo- I cated at the exact inductive center of thetransformer. This invention provides a convenient and simple arrangementwhereby the auto-transformer may be balanced in spite of inductancedifferences between the windings 6, 7, and 8. As shown in Fig. 1, a bar14 of magnetic material is located within-the core 5 and is surroundedby a few turns 15 of the terminal wire 9. The efi'ect of the flux in bar14; passing through a portion of core 5 and returning to the bar 14,upon the inductance balance of the transformer will depend upon therelative osition of .bar 14 with respect to the'win ings .6 and'7.Depending upon the position of the bar 14 the flux therefrom willproduce unequal changes of any desired degree of the flux flowingthrough the two halves of ing the the core 5 surrounded by win-dings 6and 7. A position for the adjustable bar 14: may then be readily foundin which the unequal effect upon the two halves of core 5 will serve tocorrect the differences in the induct ances of windings -6 and 7 "Whenthe most satisfactoryposition for the bar 14 has been found, the bar maybe suitably fastened so that it may be permanently retained in thatposition. 7

'Bar 14 will also serve as a path for any leakage flux from the maintransformer windings so that the leakage flux can aid the flux producedby winding 15 in correcting for the inductive unbalance of thetransformer. In some cases the leakage flux may be found to besufliciently great to correct for the inductive unbalance in which caseno winding turns will be needed on bar 14.

It is to be understood that this invention is applicable to transformersof other types than auto-transformers and furthermore that the specificembodiment above described may be variously modified without departingfrom the spirit of the invention, as defined in the appended claims.

The invention claimed is:

- 1. An inductance device comprising a substantially closed magneticcircuit core, a plurality of windings on said core, and adjust ablemeans extending across said core for increasing the leakage of thatwin-d ng ham eater inductance.

a 2. An inductance device comprising a'substantially closed magneticcircuit core, a winding onone portion of said core, a second winding ona second portion of said core, an adjustable bar of magnetic materialextending between said portions and a supplementary winding on said barand connected in circuit with said windmgs.

' 3. An inductance device comprising a substantially closed magneticcircuitvcore, independently wound windings on different parts of saidcore, and means for adjusting the relative values of the inductance ofsaid windings, said means comprising a bar of magnetic material movablerelative to said core and having one end adjacent a portion of said coresurrounded by one of said windings and having its other end adjacent aportion of said core surrounded by another of said windings, and anauxiliary winding on said bar in circuit with said other wind 1n 's. Y

Z. The method of balancing transformer 'windings wound on differentportions of a core in which a supplementary winding on a movablecorepiece "is employed connected in circuit with said windings, whichmethod comprises determining by trial that position of the movable corewith respect to the main core where the effect. of the supplementarywinding will substantially cause an inductive balance of saidtransformer windings, and securing said movable core in said poslmethodcomprises moving said bar by trial to such a position that unequalleakage losses from the two halves of said winding produced by said barcause the connection to be located approximately at the inductive centerof said winding, and securing said movable core in said position.

In wltness whereof, I hereunto subscribe my name this 14th day of AprilA. D., 1922.

FRANK E. FIELD}

